The document provides an overview of terpenoids, highlighting their definition as phyto constituents derived from isoprene molecules, with a molecular formula of C5H8. It details the classification of terpenoids into monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, and polyterpenoids, along with examples of each. Additionally, the document mentions that terpenoids exhibit biological activities, making them useful in pharmaceuticals for applications such as insecticidal, anthelmintic, and antiseptic actions.